Light reaction mass actuator

Abstract

A very light, high force reaction-mass actuator using high energy density magnetostrictive material to accelerate a mass, producing a reaction force that can be used to oppose vibration forces. The reaction-mass actuator is configured having an axially symmetric design that features a Terfenol-D rod as a core. Surrounding the rod is a magnetic coil which provides the changing magnetizing field used to actively control magnetostrictive strain of the Terfenol rod. The magnetic coil also provides a magnetic flux based on a D.C. current, for biasing the Terfenol rod. The magnetic coil, disposed about the fixed magnetostrictive rod, is incorporated into a reaction mass assembly that is suspended and sealed inside an enclosed, stiff outer shell or housing by an elastomeric material mounting configuration that facilitates an output force with suppressed harmonic content. In addition, the elastomeric mounting configuration provides sealing protection against external factors. In one embodiment, the magnetic coil is wound on a bobbin effecting a movable mass that is accelerated to produce a force on a mounting surface. The Terfenol rod is placed under axially compressive stress by a simple mechanical preloading mechanism. This increases strain in the Terfenol rod while providing a return spring for the reaction mass when it has reached its maximum stroke.